This laboratory utilizes two equine herpesviruses as models of herpesvirus infection. Equine herpesvirus type 1 (EHV-1) is responsible for "abortion storms" in herds of pregnant mares, and equine herpesvirus type 2 (equine cytomegalovirus; ECMV) establishes a chronic infection in horses. These two viruses differ in several biological and physical properties: (1) EHV-1 has a highly lytic infection whereas ECMV has a very slowly developing cytopathology; (2) EHV-1 and ECMV have genomes of 92 md and 120 md, respectively; and (3) the EHV-1 genome has one unique short region (22 md) flanked by repeat regions that allow the DNA to exist in two isomeric forms; the ECMV genome has two unique short regions (6 md and 8 md each) that are flanked by repeat regions. These viruses do share genetic homology and are capable of establishing persistent infections and oncogenically transformed cell lines. All EHV-1 and ECMV transformed and tumor cells express viral polypeptides and contain viral sequences. The EHV-1 sequences present in transformed cells are integrated and are amplified by tandem duplications during tumorigenesis. ECMV transformed and tumor cells retain viral specific sequences. Virtually nothing is known about the viral transcriptional process in lytically infected cells and nothing is known about the viral transcripts present within oncogenically transformed or tumor cells or persistently infected cells. To fill this void in our understanding of equine herpesvirus infections, the goals of this proposal are: (1) to continue to fine map the immediate early transcripts produced in EHV-1 and ECMV lytic infections by the S1 nuclease method and to determine whether post-transcriptional processing, such as splicing, occurs; (2) to compare the transcriptional processes in EHV-1 and ECMV lytic infections in order to identify common or unique transcriptional strategies; (3) to identify and isolate viral transcripts from EHV-1 and ECMV oncogenically transformed cells and tumor cells; (4) to identify and isolate viral transcripts from EHV persistently infected-oncogenically transformed cell lines; and (5) to analyze viral transcripts from oncogenically transformed cells by RE, hybridization, S1 nuclease and DNA sequencing methodologies. This information will be compared to data obtained in lytically infected cells in an attempt to identify alterations in virus transcription that modulate lytic infections and thus lead to oncogenic transformation/persistent infection.